How to transform a key/value string into distinct rows?

Question

I have a R dataset with key value strings which looks like below:

quest<-data.frame(city=c(\"Atlanta\",\"New York\",\"Atlanta\",\"Tampa\"), key_value=c(\"rev=         


        

Answer 1

Split by ;, then by = and |, and combine into a matrix, using the first part as the name. Then repeat the rows of the original data frame by however many rows were found for each, and combine. I don't convert here any columns to numeric, they're left as character.

a <- strsplit(as.character(quest$key_value), ";")
a <- lapply(a, function(x) {
    x <- do.call(cbind, strsplit(x, "[=|]"))
    colnames(x) <- x[1,]
    x[-1,,drop=FALSE]
})
b <- quest[rep(seq_along(a), sapply(a, nrow)), colnames(quest) != "key_value", drop=FALSE]
out <- cbind(b, do.call(rbind, a), stringsAsFactors=FALSE)
rownames(out) <- NULL
out
##       city   rev qty   zip
## 1  Atlanta    63   1 45987
## 2 New York 10.60   1 12686
## 3 New York    34   2 12694
## 4  Atlanta    12   1 74268
## 5    Tampa     3   1 33684
## 6    Tampa    24   6 36842
## 7    Tampa     8   3 30254